1. Technical Field
The invention relates generally to an optical amplifiers and methods and apparatus that use optical amplifiers.
2. Discussion of the Related Art
This section introduces aspects that may be helpful to facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
In many optical communication systems, the data-modulated optical carrier undergoes amplification between the optical transmitter and the optical receiver. One type of optical amplification involves conversion of a data-modulated optical carrier from an optical signal to an electrical signal and a re-conversion of a corresponding electrical back to an optical signal. Such a conversion and re-conversion sequence is typically referred to as optical to electrical to optical (OEO) type of signal processing. Another type of optical amplification involves amplification of the data-modulated optical carrier in the optical domain without any type of OEO signal procession. This later type of optical amplification is often referred to as all-optical amplification. All-optical amplification has been performed using pumped rare-earth dopants and using optical waveguides pumped to cause Raman-type optical processes.
In long-distance optical communication systems, OEO and/or all-optical amplification is often needed to compensate for attenuation of the data-modulated optical carrier in passive optical transmission fibers.